U.S. patent number 10,882,513 [Application Number 16/518,946] was granted by the patent office on 2021-01-05 for hybrid vehicle.
This patent grant is currently assigned to Honda Motor Co., Ltd.. The grantee listed for this patent is Honda Motor Co., Ltd.. Invention is credited to Hisashi Ito, Kentaro Onuma, Hidenori Sakai.
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United States Patent |
10,882,513 |
Onuma , et al. |
January 5, 2021 |
Hybrid vehicle
Abstract
A hybrid vehicle is provided. A vehicle V has a gasoline
particulate filter (GPF) provided on an exhaust passage to capture
particulate matter (PM) included in exhaust, a generator motor
connected to a crank shaft of an engine, an exhaust temperature
sensor acquiring a filter temperature correlated with a temperature
of the GPF, and an electronic control unit (ECU) performing motor
drive control for rotating the crank shaft with the generator motor
when a filter temperature is higher than or equal to a PM
combustion start temperature and a PM combustion integration amount
that is an integration amount of PM combusted in the GPF is less
than a PM discharge integration amount.
Inventors: |
Onuma; Kentaro (Saitama,
JP), Ito; Hisashi (Saitama, JP), Sakai;
Hidenori (Saitama, JP) |
Applicant: |
Name |
City |
State |
Country |
Type |
Honda Motor Co., Ltd. |
Tokyo |
N/A |
JP |
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Assignee: |
Honda Motor Co., Ltd. (Tokyo,
JP)
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Family
ID: |
1000005281123 |
Appl.
No.: |
16/518,946 |
Filed: |
July 22, 2019 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20200031333 A1 |
Jan 30, 2020 |
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Foreign Application Priority Data
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Jul 24, 2018 [JP] |
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2018-138308 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F01N
9/002 (20130101); B60W 20/40 (20130101); B60W
2510/068 (20130101) |
Current International
Class: |
B60W
20/40 (20160101); F01N 9/00 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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2005048740 |
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Feb 2005 |
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JP |
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2017136935 |
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Aug 2017 |
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JP |
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2018083570 |
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May 2018 |
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JP |
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Other References
"Office Action of Japan Counterpart Application", dated Jul. 21,
2020, with English translation thereof, p. 1-p. 6. cited by
applicant .
"Office Action of Japan Counterpart Application," with machine
English translation thereof, dated Jan. 14, 2020, p. 1-p. 8. cited
by applicant.
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Primary Examiner: Gurari; Erez
Attorney, Agent or Firm: JCIPRNET
Claims
What is claimed is:
1. A hybrid vehicle comprising: a filter provided on an exhaust
passage of an engine to capture particulate matter included in
exhaust; a motor connected to an output shaft of the engine; a
temperature acquisition part acquiring a filter correlation
temperature correlated with a temperature of the filter; and a
control part performing motor drive control for rotating the output
shaft with the motor when the filter correlation temperature is
higher than or equal to a reference temperature and a particulate
matter combustion amount that is an integration amount of the
particulate matter combusted in the filter is smaller than a
combustion amount threshold.
2. The hybrid vehicle according to claim 1, wherein the control
part assumes that an allowable upper limit amount of particulate
matter has been deposited in the filter, and calculates a
combustion integration amount of particulate matter combusted from
a start of the engine in the filter as the particulate matter
combustion amount.
3. The hybrid vehicle according to claim 2, wherein the control
part calculates the particulate matter combustion amount based on
the filter correlation temperature and an operation state of the
engine.
4. The hybrid vehicle according to claim 1, wherein the control
part calculates a discharge integration amount of particulate
matter discharged from a start of the engine as the combustion
amount threshold.
5. The hybrid vehicle according to claim 2, wherein the control
part calculates a discharge integration amount of particulate
matter discharged from a start of the engine as the combustion
amount threshold.
6. The hybrid vehicle according to claim 3, wherein the control
part calculates a discharge integration amount of particulate
matter discharged from a start of the engine as the combustion
amount threshold.
7. The hybrid vehicle according to claim 4, wherein the control
part calculates the combustion amount threshold based on an engine
RPM, an intake air amount, and an engine water temperature.
8. The hybrid vehicle according to claim 1, wherein, when a
start-time water temperature that is an engine water temperature at
a time of a start of the engine is in a predetermined
temperature-rise range, the control part executes temperature rise
control for raising temperatures of the engine and exhaust of the
engine, and when the start-time water temperature is equal to or
lower than a lower limit of the temperature-rise range, the control
part executes the motor drive control.
9. The hybrid vehicle according to claim 2, wherein, when a
start-time water temperature that is an engine water temperature at
a time of a start of the engine is in a predetermined
temperature-rise range, the control part executes temperature rise
control for raising temperatures of the engine and exhaust of the
engine, and when the start-time water temperature is equal to or
lower than a lower limit of the temperature-rise range, the control
part executes the motor drive control.
10. The hybrid vehicle according to claim 3, wherein, when a
start-time water temperature that is an engine water temperature at
a time of a start of the engine is in a predetermined
temperature-rise range, the control part executes temperature rise
control for raising temperatures of the engine and exhaust of the
engine, and when the start-time water temperature is equal to or
lower than a lower limit of the temperature-rise range, the control
part executes the motor drive control.
11. The hybrid vehicle according to claim 4, wherein, when a
start-time water temperature that is an engine water temperature at
a time of a start of the engine is in a predetermined
temperature-rise range, the control part executes temperature rise
control for raising temperatures of the engine and exhaust of the
engine, and when the start-time water temperature is equal to or
lower than a lower limit of the temperature-rise range, the control
part executes the motor drive control.
12. The hybrid vehicle according to claim 5, wherein, when a
start-time water temperature that is an engine water temperature at
a time of a start of the engine is in a predetermined
temperature-rise range, the control part executes temperature rise
control for raising temperatures of the engine and exhaust of the
engine, and when the start-time water temperature is equal to or
lower than a lower limit of the temperature-rise range, the control
part executes the motor drive control.
13. The hybrid vehicle according to claim 8, wherein the control
part estimates a deposition amount of particulate matter in the
filter and performs the motor drive control until the deposition
amount becomes equal to or smaller than an end threshold when the
deposition amount exceeds a start threshold in a state where the
start-time water temperature is higher than or equal to the lower
limit of the temperature-rise range.
14. The hybrid vehicle according to claim 1, wherein the engine is
a gasoline engine using gasoline as a fuel.
15. The hybrid vehicle according to claim 2, wherein the engine is
a gasoline engine using gasoline as a fuel.
16. The hybrid vehicle according to claim 3, wherein the engine is
a gasoline engine using gasoline as a fuel.
17. The hybrid vehicle according to claim 4, wherein the engine is
a gasoline engine using gasoline as a fuel.
18. The hybrid vehicle according to claim 5, wherein the engine is
a gasoline engine using gasoline as a fuel.
19. The hybrid vehicle according to claim 6, wherein the engine is
a gasoline engine using gasoline as a fuel.
20. The hybrid vehicle according to claim 1, wherein the control
part executes the motor drive control at least under conditions
that a travel range is a forward range, a vehicle speed is higher
than or equal to a predetermined reference vehicle speed, and a
required driving force is smaller than a predetermined reference
driving force.
Description
CROSS-REFERENCE TO RELATED APPLICATION
This application claims the priority of Japan patent application
serial no. 2018-138308, filed on Jul. 24, 2018. The entirety of the
above-mentioned patent application is hereby incorporated by
reference herein and made a part of this specification.
BACKGROUND
Technical Field
The present disclosure relates to a hybrid vehicle. More
specifically, the disclosure relates to a hybrid vehicle with a
filter that traps particulate matter included in exhaust of an
engine and a motor connected to the output shaft of the engine.
Description of Related Art
A vehicle in which an engine functioning as a driving force
generation source is mounted has a filter that traps particulate
matter (which may be abbreviated as "PM" below) included in exhaust
of the engine (refer to Patent Document 1 (Japanese Patent
Laid-Open Publication No. 2017-136935)). PM trapped by the filter
is appropriately combusted and removed by the high-temperature
exhaust while the vehicle travels.
When PM trapped by the filter is combusted, the temperature of the
filter increases accordingly. However, the highest temperature of
the filter at that time becomes higher as the amount of PM
deposited in the filter becomes larger and the concentration of
oxygen included in the exhaust flowing into the filter due to the
fuel cutting function or the like becomes higher. Thus, if the PM
which has been deposited in the filter in a larger amount than a
predetermined allowable upper limit (which will be referred to as
an "excessive deposition state") is combusted, the temperature of
the filter rises higher than the guaranteed temperature and there
is concern of the filter undergoing melting damage. Thus, a vehicle
that performs excessive deposition prevention control has been
recently proposed to avoid deposition of a larger amount of PM than
the determined allowable upper limit that has been set to prevent
melting damage of the filter.
However, when the fuel cutting function caused by deceleration is
executed, new air including a large amount of oxygen flows into the
filter having a high temperature due to acceleration, and thus PM
deposited in the filter is combusted and the amount of PM deposited
in the filter decreases. Thus, a vehicle performing the fuel
cutting function of the engine when it decelerates need not
actively perform the above-described excessive deposition
prevention control. However, hybrid vehicles having both an engine
and a motor as a driving force generation source have fewer chances
of executing the fuel cutting function than normal vehicles only
having an engine as a driving force generation source. For this
reason, hybrid vehicles tend to have a larger amount of PM retained
in filters than normal vehicles, and thus are particularly required
to execute the excessive deposition prevention control.
Patent Document 1 proposes a hybrid vehicle tending to have a large
amount of deposited PM that stops fuel injection of the engine and
causes the motor to rotate the output shaft of the engine when a
temperature of the filter is higher than or equal to a
predetermined reference temperature. Accordingly, new air absorbed
into the engine in the non-combustion state is supplied to the
filter having the reference temperature or higher, the PM trapped
by the filter is removed by combustion, and thus excessive
deposition in the filter can be prevented.
PATENT DOCUMENTS
[Patent Document 1] Japanese Patent Laid-Open Publication No.
2017-136935
Patent Document 1, however, does not sufficiently consider a timing
appropriate for executing idle run control of the engine using the
motor. In other words, in the disclosure of Patent Document 1, idle
run control is performed when the filter is at the reference
temperature or higher. Thus, according to the disclosure of the
Patent Document 1, while excessive deposition can be prevented,
idle run control is performed more frequently than necessary, and
thus there is concern of energy such as a fuel or electric power
being wasted.
SUMMARY
A hybrid vehicle according to the present disclosure (e.g., the
vehicle V which will be described below) has a filter (e.g., the
gasoline particulate filter (GPF) 33 which will be described below)
provided on an exhaust passage (e.g., the exhaust pipe 32 which
will be described below) of an engine to capture particulate matter
included in exhaust, a motor (e.g., the generator motor GM which
will be described below) connected to an output shaft (e.g., the
crank shaft 17 which will be described below) of the engine, a
temperature acquisition part (e.g., the exhaust temperature sensor
43 and the electronic control unit (ECU) 7 which will be described
below) acquiring a filter-correlated temperature correlated with a
temperature of the filter, and a control part (e.g., the ECU 7
which will be described below) performing motor drive control for
rotating the output shaft with the motor when the filter-correlated
temperature is higher than or equal to a reference temperature and
a particulate matter combustion amount that is an integration
amount of particulate matter combusted in the filter is smaller
than a combustion amount threshold.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a diagram illustrating a configuration of a vehicle
according to an embodiment of the present disclosure.
FIG. 2 is a diagram illustrating a configuration of an engine and
an exhaust purification system thereof.
FIG. 3 is a diagram illustrating the relationship between the PM
deposition amount and travel distance.
FIG. 4 is a flowchart showing the detailed procedure for excessive
deposition prevention control.
FIG. 5 is a diagram illustrating temporal changes of the
accumulation amount of PM discharged from the engine.
FIG. 6 is a diagram illustrating the detailed procedure for
calculating the estimated PM deposition amount.
FIG. 7 is a flowchart showing the detailed procedure for all-time
excessive deposition prevention control.
FIG. 8 is a flowchart showing the detailed procedure for start-time
excessive deposition prevention control.
FIG. 9 is a diagram illustrating the detailed procedure for
calculating a PM combustion integration amount.
FIG. 10 is a diagram illustrating the detailed procedure for
calculating a PM discharge integration amount.
FIG. 11 is a time chart illustrating a specific example of
excessive deposition prevention control.
DESCRIPTION OF THE EMBODIMENTS
The disclosure provides a hybrid vehicle that can perform idle run
control of the engine for preventing excessive deposition at proper
timings without wasting energy such as a fuel or electric
power.
According to an embodiment, the control part may assume that an
allowable upper limit amount of particulate matter has been
deposited in the filter and calculate a combustion integration
amount of particulate matter combusted from a start of the engine
in the filter as the particulate matter combustion amount.
According to the embodiment, the control part may calculate the
particulate matter combustion amount based on the filter-correlated
temperature and an operation state of the engine.
According to the embodiment, the control part may calculate a
discharge integration amount of particulate matter discharged from
a start of the engine as the combustion amount threshold.
According to the embodiment, the control part may calculate the
combustion amount threshold based on an engine RPM, an intake air
amount, and an engine water temperature.
According to the embodiment, when a start-time water temperature
that is an engine water temperature at a time of a start of the
engine is in a predetermined temperature-rise range, the control
part may execute temperature rise control for raising temperatures
of the engine and exhaust of the engine, and when the start-time
water temperature is equal to or lower than a lower limit of the
temperature-rise range, the control part may execute the motor
drive control.
According to the embodiment, the control part may estimate a
deposition amount of particulate matter of the filter and perform
the motor drive control until the deposition amount becomes equal
to or smaller than an end threshold when the deposition amount
exceeds a start threshold in a state where the start-time water
temperature is higher than or equal to the lower limit of the
temperature-rise range.
According to the embodiment, the engine may be a gasoline engine
using gasoline as a fuel.
According to the embodiment, the control part may execute the motor
drive control at least under conditions that a travel range is a
forward range, a vehicle speed is higher than or equal to a
predetermined reference vehicle speed, and a required driving force
is smaller than a predetermined reference driving force.
Some of particulate matter discharged from the engine and captured
by the filter that has not been combusted with heat of exhaust is
deposited in the filter. Thus, it is important to know the amount
of the particulate matter combusted in the filter in order to
prevent excessive deposition in the filter with efficiency.
Therefore, the hybrid vehicle of the present disclosure performs
the motor drive control for rotating the output shaft of the engine
with the motor when the filter-correlated temperature is higher
than or equal to the reference temperature and the particulate
matter combustion amount that is an integration amount of
particulate matter combusted in the filter is smaller than the
combustion amount threshold. Accordingly, the motor drive control
is executed when the particulate matter combustion amount is
smaller than the combustion amount threshold, that is, particulate
matter needs to be actively combusted to prevent excessive
deposition, and the combustion of the particulate matter deposited
in the filter can be promoted. In addition, the motor drive control
can be prevented from being performed when the particulate matter
combustion amount is greater than or equal to the combustion amount
threshold, that is, most particulate matter captured in the filter
has already been combusted and thus excessive deposition will not
occur. Accordingly, waste of energy such as a fuel and electric
power for executing the motor drive control can be curbed.
Particulate matter particularly increases immediately after a start
of the engine and is discharged from the engine. Thus, the control
part calculates the combustion integration amount of particulate
matter combusted in the filter immediately after the start of the
engine when a particularly large amount of particulate matter can
be discharged, sets the amount as the particulate matter combustion
amount, and determines a timing at which the motor drive control is
executed based on the particulate matter combustion amount.
Accordingly, the motor drive control can be executed at the right
time, and further waste of energy needed for executing the motor
drive control can be curbed. In addition, in the present
disclosure, the control part assumes that the allowable upper limit
amount of particulate matter has been deposited in the filter when
calculating the particulate matter combustion amount. As the
deposition amount of particulate in the filter increases, the
amount of particulate matter combusted in the filter increases as
described above, and thus the particulate matter combustion amount
is estimated to be greater than the actual amount. Thus, according
to the present disclosure, the execution frequency of the motor
drive control is lower than when the particulate matter combustion
amount is calculated using the actual particulate matter deposition
amount, and thus waste of energy such as a fuel and electric power
for executing the motor drive control can be curbed accordingly.
However, while there is concern of the particulate matter
deposition amount increasing in the filter due to the low execution
frequency of the motor drive control in this case, the particulate
matter combustion amount is calculated on the assumption that the
allowable upper limit amount of particulate matter has been
deposited in the filter according to the present disclosure as
described above, and thus it is possible to prevent the actual
deposition amount from exceeding the allowable upper limit
amount.
According to the embodiment, the control part may calculate the
particulate matter combustion amount based on the filter-correlated
temperature correlated with the particulate matter combustion
amount and an operation state of the engine. Accordingly, since the
particulate matter combustion amount can be calculated with high
accuracy, the motor drive control can be executed at the right
time, and further waste of energy needed for executing the motor
drive control can be curbed.
As will be described below with reference to FIG. 5, the discharge
integration amount of particulate matter discharged from the start
of the engine significantly increases in the process of warm-up of
the engine. Thus, the control part may set the discharge
integration amount of particulate matter discharged from the start
of the engine as the combustion amount threshold that is the
threshold with respect to the particulate matter combustion amount.
Accordingly, the motor drive control can be executed at the right
time in the process of warm-up of the engine in which the
deposition amount is likely to significantly increase.
According to the embodiment, the control part may calculate the
combustion amount threshold that is the discharge integration
amount of the particulate matter discharged from the start of the
engine based on an engine RPM, an intake air amount, and an engine
water temperature. Accordingly, since the combustion amount
threshold can be calculated with high accuracy, the motor drive
control can be executed at the right time, and further waste of
energy needed for executing the motor drive control can be
curbed.
According to the embodiment, when the start-time water temperature
is in the predetermined temperature-rise range, the control part
may execute temperature rise control, and thereby temperatures of
the engine and exhaust of the engine are raised and further exhaust
purification performance of the exhaust purification device is
improved. In addition, when such temperature rise control is
executed, the temperature of the exhaust increases, and thus
particulate matter captured in the filter is combusted accordingly.
However, when the start-time water temperature is excessively low,
more specifically, when the start-time water temperature is lower
than the lower limit of the temperature-rise range, it is difficult
to improve the exhaust purification performance in an early stage
even if the temperature rise control is performed, there is concern
of fuel efficiency deteriorating, and therefore the control part
does not execute the temperature rise control. Thus, when the
start-time water temperature is equal to or lower than the lower
limit of the temperature-rise range and the temperature rise
control is not executed, the control part performs the motor drive
control. Accordingly, excessive deposition in the filter can be
prevented at the time of a low-temperature start of the vehicle at
which the deposition amount of particulate matter easily increases
in the filter.
When the start-time water temperature is in the predetermined
temperature-rise range as described above, while the temperature
rise control is executed, the deposition amount of particulate
matter in the filter may gently increase and exceed the allowable
upper limit amount. Thus, when the deposition amount exceeds the
start threshold in a state in which the start-time water
temperature is higher than or equal to the lower limit of the
temperature-rise range, the control part performs the motor drive
control until the deposition amount becomes equal to or smaller
than the end threshold. Accordingly, it is possible to prevent the
deposition amount from greatly exceeding the allowable upper limit
amount.
Since gasoline engines have a higher exhaust temperature than
diesel engines, the deposition amount of particulate matter of the
filter tends to converge on a predetermined saturated deposition
amount even if a forced regeneration process as in DPFs used in
diesel engines is not periodically performed. However, since the
chances for hybrid vehicles in which gasoline engines are mounted
to execute fuel cutting to promote combustion of particulate
matters as described above are limited, the saturated deposition
amount may exceed the allowable upper limit amount that is
determined to prevent melting damage of the filter. With respect to
this, the control part performs the motor drive control for
rotating the output shaft of the engine with the motor when the
filter-correlated temperature is higher than or equal to the
reference temperature and the particulate matter combustion amount
is smaller than the combustion amount threshold. Accordingly, the
motor drive control can be performed at the right timing to prevent
the saturated deposition amount from exceeding the allowable upper
limit amount.
When the travel range is not the forward range, or the vehicle
speed is lower than the reference vehicle speed, a sufficient
amount of air is not supplied to the filter even if the motor drive
control is executed, and the effect of combusting particulate
matter is small. In addition, since it is difficult to generate a
driving force with the engine in the motor drive control, if the
motor drive control is executed in a state in which a required
driving force is greater than the reference driving force, a
driving force according to the required driving force may not be
generated and power performance of the vehicle may deteriorate.
Thus, the control part executes the motor drive control on the
condition that the travel range is the forward range, the vehicle
speed is higher than or equal to the predetermined reference
vehicle speed, and the required driving force is smaller than the
predetermined reference driving force. Accordingly, the motor drive
control can be executed without lowering the power performance of
the vehicle, and particulate matter can be effectively combusted
through the motor drive control.
An embodiment of the present disclosure will be described below
with reference to the drawings. FIG. 1 is a diagram illustrating a
configuration of a vehicle V according to the present embodiment.
The vehicle V is a so-called hybrid vehicle having an engine 1 and
a drive motor TM as driving force generation sources. More
specifically, the vehicle V has the engine 1, a generator motor GM
connected to the output shaft of the engine 1, a clutch C that
connects and disconnects the output shaft of the engine 1 to and
from drive wheels W, the drive motor TM with an output shaft
connected to the drive wheels W, and a battery B that exchanges
electric power with the drive motor TM via an inverter, a
converter, or the like which is not illustrated.
The vehicle V can travel broadly in three travel modes which are EV
travel, series travel, and engine travel modes.
In the EV travel mode, the vehicle V travels by driving the drive
motor TM with electric power supplied from the battery B. During
the EV travel mode, basically the engine 1 and the generator motor
GM stop.
In the series travel mode, the vehicle V causes the clutch C to
disconnect the engine 1 from the drive wheels W and causes the
engine 1 to drive the generator motor GM. In addition, in the
series travel mode, the electric power from the battery B and
electric power generated by the generator motor GM described above
are supplied to the drive motor TM.
In the engine travel mode, the vehicle V travels by causing the
clutch C to connect the engine 1 and the drive wheels W and causing
the engine 1 to drive the drive wheels W.
The travel mode of the vehicle V is basically set to the EV travel
mode to perform deceleration regeneration with the drive motor TM
when the vehicle decelerates, and the engine 1 stops. For this
reason, the engine 1 of the vehicle V which is a hybrid vehicle has
fewer chances to perform deceleration fuel cutting than normal
vehicles having engines as the only driving force generation
source.
FIG. 2 is a diagram illustrating a configuration of the engine 1
and an exhaust purification system 2 thereof. The exhaust
purification system 2 has the generator motor GM connected to the
crank shaft 17 that is the output shaft of the engine 1 and an
electronic control unit 7 (which will be referred to as "ECU 7"
below) that controls the engine 1 and the generator motor GM.
The engine 1 is a multi-cylinder gasoline engine using gasoline as
a fuel and having multiple cylinders 11 (only one is illustrated in
FIG. 2). The engine 1 has a piston 12 provided in each cylinder 11,
a fuel injection valve 13, and a spark plug 14 provided for each
cylinder 11, an intake valve 15 provided at an intake port
communicating with each cylinder 11, an intake pipe 31 guiding air
to the intake port, an exhaust valve 16 provided in an exhaust port
communicating with each cylinder 11, an exhaust pipe 32 in which
exhaust flowing out from the exhaust port flows, and the crank
shaft 17 linked to the piston 12 via a connecting rod.
The engine 1 has an intake cam shaft 18 and an exhaust cam shaft 19
connected to the crank shaft 17 via a timing belt and rotating
according to rotation of the crank shaft 17. More specifically, the
cam shafts 18 and 19 are designed to rotate once when the crank
shaft 17 rotates twice. An intake cam driving opening and closing
of the intake valve 15 is provided in the intake cam shaft 18, and
an exhaust cam driving opening and closing of the exhaust valve 16
is provided in the exhaust cam shaft 19. Accordingly, when the cam
shafts 18 and 19 rotate, the intake valve 15 and the exhaust valve
16 advance and retract (open and close) according to the profile of
the cams provided in the cam shafts 18 and 19.
The exhaust pipe 32 has an exhaust particulate filter (which will
be abbreviated as "GPF" below) that captures PM included in the
exhaust of the gasoline engine. The GPF 33 is, for example, a wall
flow type having a plurality of cells formed to be compartmented by
a plurality of porous walls. That is, the GPF 33 captures PM in
such a way that PM is deposited on the surfaces of the porous walls
when the exhaust passes through the fine pores inside the porous
walls. In addition, the porous walls of the GPF 33 support, for
example, a three-way catalyst for purifying CO, HC, and NO.sub.X
included in the exhaust.
Here, the relationship between the PM deposition amount [g] that is
the deposition amount of PM in the GPF 33 and the travel distance
will be described with reference to FIG. 3. FIG. 3 is a diagram
illustrating the relationship between PM deposition amount and
travel distance. In FIG. 3, the solid line represents the change in
the PM deposition amount of the GPF mounted in the hybrid vehicle
of the present embodiment, and the dashed line represents the
change in the PM deposition amount of the GPF mounted in a normal
vehicle only having an engine as a driving force generation
source.
As illustrated in FIG. 3, the PM deposition amount of the GPF
increases as the travel distance becomes longer. More specifically,
while the travel distance is short, that is, the PM deposition
amount is small, the PM deposition amount increases substantially
in proportion to the travel distance, and the PM deposition amount
tends toward a predetermined constant amount as the travel distance
becomes longer. The reason for this is as follows.
First, although the GPF captures substantially all PM discharged
from the engine 1, some of the PM captured by the GPF is combusted
due to heat of the discharge. Thus, if the amount of PM discharged
from the engine per unit time is set to a PM discharge amount [g/s]
and the amount of PM combusted in the GPF per unit time is set to a
PM combustion amount [g/s], it is considered that, when the PM
discharge amount is greater than the PM combustion amount, the PM
deposition amount increases in proportion to the travel distance,
and when the PM discharge amount is substantially equal to the PM
combustion amount, the PM deposition amount is constant regardless
of an increase of the travel distance. That is, since the PM
combustion amount in the GPF increases as the PM deposition amount
increases, the PM deposition amount is considered to converge on a
fixed amount (which will also be referred to as a "saturated
deposition amount" below) as the travel distance becomes
longer.
In addition, the saturated deposition amount of the PM deposition
amount of the GPF mounted in the hybrid vehicle (see the thick
solid line in FIG. 3) is greater than the saturated deposition
amount of the PM deposition amount of the GPF mounted in the normal
vehicle (see the thick dashed line in FIG. 3) as illustrated in
FIG. 3. That is, the GPF mounted in the hybrid vehicle is more
stable than the GPF mounted in the normal vehicle when a great
amount of PM is deposited. The reason for this is as follows.
The PM combustion amount of the GPF is considered to increase as
the concentration of oxygen in exhaust becomes higher. Thus, when
the fuel cutting function of temporarily setting a fuel injection
amount of the engine 1 to 0 at the time of deceleration is
executed, new air including a large amount of oxygen flows into the
GPF that has been heated at the time of acceleration, and thus the
PM combustion amount increases. On the other hand, since the hybrid
vehicle of the present embodiment performs regenerative driving
using the drive motor TM at the time of deceleration, it executes
the fuel cutting function less frequently than normal vehicles.
Thus, the hybrid vehicle has a smaller PM combustion amount than
normal vehicles, and therefore the saturated deposition amount of
the PM deposition amount thereof is considered to be greater.
The PM deposition amount of the GPF 33 mounted in the vehicle V
which is a hybrid vehicle described above tends to be greater than
the PM deposition amount of the GPF mounted in the normal vehicle,
and thus the PM deposition amount is likely to be in an excessive
deposition state in which the deposition amount exceeds a
predetermined allowable upper limit set to prevent melting damage
of the GPF. In addition, there is concern of the GPF 33 suffering
melting damage as described above when the GPF 33 is in the
excessive deposition state. Thus, the ECU 7 prevents the GPF 33
from being in the excessive deposition state by supplying new air
including a large amount of oxygen to the GPF 33 at the right
timing and performing excessive deposition prevention control for
promoting combustion of PM deposited in the GPF 33 as will be
described below with reference to FIG. 4.
Returning to FIG. 2, the crank shaft 17 of the engine 1 is
connected to the output shaft of the generator motor GM via a power
transmission mechanism, which is not illustrated. Thus, in the
series travel mode, the vehicle can be caused to travel by the
engine 1 driving the generator motor GM and supplying the electric
power generated by the generator motor GM to the drive motor
TM.
In addition, at the time of deceleration of the vehicle, fuel
injection from the fuel injection valve 13 is stopped, the electric
power stored in the battery B is supplied to the generator motor
GM, and motor drive control for rotating the crank shaft 17 of the
engine 1 with the generator motor GM is executed. Accordingly, air
including a large amount of oxygen is supplied from the intake pipe
31 to the GPF 33 on the exhaust pipe 32 due to pumping of the
piston 12, and thus combustion of PM deposited in the GPF 33 can be
promoted.
In addition, the vehicle V has a plurality of sensors 41 to 43 for
detecting states of the engine 1, the GPF 33, and the like.
The water temperature sensor 41 detects a temperature of cooling
water for cooling the engine 1 and transmits a signal according to
the detected value to the ECU 7. The ECU 7 acquires the engine
water temperature [.degree. C.] that is the cooling water
temperature of the engine 1 by using the detection signal of the
water temperature sensor 41.
The vehicle speed sensor 42 transmits a pulse signal according to
the rotation speed of the vehicle shaft connected to the drive
wheels W to the ECU 7. The ECU 7 calculates the vehicle speed
[km/h] of the vehicle V by using the pulse signal transmitted from
the vehicle speed sensor 42.
The exhaust temperature sensor 43 is provided on the downstream
side of the GPF 33 on the exhaust pipe 32. The exhaust temperature
sensor 43 detects a temperature of exhaust flowing out from the GPF
33 and transmits a signal according to the detected value to the
ECU 7. The ECU 7 acquires the temperature of the exhaust flowing
out from the GPF 33 by using the detection signal of the exhaust
temperature sensor 43 and further estimates a filter temperature
that is a temperature of the GPF 33 through an arithmetic
operation, which is not illustrated, based on the temperature of
the exhaust. Therefore, a temperature acquisition unit of the
present embodiment is constituted by the exhaust temperature sensor
43 and the ECU 7.
Further, although the filter temperature is estimated by using the
detection signal of the exhaust temperature sensor 43 in the
present embodiment, the present disclosure is not limited thereto.
For example, the filter temperature may be directly acquired by
providing a temperature sensor that is in direct contact with the
GPF 33.
FIG. 4 is a flowchart showing the detailed procedure for excessive
deposition prevention control for preventing excessive deposition
in the GPF 33. The excessive deposition prevention control of FIG.
4 is repeatedly executed by the ECU 7 in a driving cycle from when
the vehicle is started according to an operation of an ignition
switch, which is not illustrated, by a driver until the vehicle is
stopped according to another operation of the ignition switch
thereafter in every predetermined control period.
FIG. 5 is a graph showing temporal changes of the integration
amount [g] of PM discharged from the engine 1 in travel modes
indicated by fine lines. FIG. 5 illustrates the temporal changes of
the integration amount of PM in a case in which the engine water
temperature when the engine is started (which will be referred to
as a "start-time water temperature" below) is changed to
-15.degree. C., -20.degree. C., and -30.degree. C. with different
types of lines.
As illustrated in FIG. 5, the integration amount of PM sharply
increases immediately after the engine 1 is started at the time t0
and then gently increases from the time t1 at which warm-up of the
engine 1 is completed. That is, the amount of PM discharged from
the engine 1 after warm-up is sufficiently smaller than the amount
of PM discharged from the engine 1 before warm-up is completed. In
addition, as illustrated in FIG. 5, the integration amount of PM
discharged until warm-up of the engine 1 is completed increases as
the start-time water temperature becomes lower. Since the
integration amount of PM discharged from the engine 1 is more
likely to increase immediately after the start of the engine,
particularly in a low-temperature environment as described above,
the vehicle easily enters the excessive deposition state. For this
reason, the excessive deposition prevention control according to
the present embodiment is constituted by start-time excessive
deposition prevention control (see S10) for executing the motor
drive control focusing on the time immediately after the start of
the engine at which the filter easily enters the excessive
deposition state and all-time excessive deposition prevention
control (see S5) for executing the motor drive control regardless
of a time when the PM deposition amount increases as illustrated in
FIG. 4.
First, in S1, the ECU 7 calculates an estimated PM deposition
amount [g] corresponding to the estimated value of the current PM
deposition amount in the GPF, and the process proceeds to S2.
FIG. 6 is a diagram illustrating the detailed procedure for
calculating the estimated PM deposition amount by the ECU 7. The
ECU 7 includes a discharge amount estimation unit 71 that
calculates an estimated PM discharge amount [g/s] corresponding to
the estimated value of the PM discharge amount, a combustion amount
estimation unit 72 that calculates an estimated PM combustion
amount [g/s] corresponding to the estimated value of the PM
combustion amount, and an integration unit 73 that calculates an
estimated PM deposition amount by integrating the difference
between the calculated estimated PM discharge amount and estimated
PM combustion amount. The ECU 7 calculates the estimated PM
deposition amount by repeatedly executing calculation with the
discharge amount estimation unit 71, the combustion amount
estimation unit 72, and the integration unit 73 in every
predetermined control period.
The PM discharge amount changes according to the operation state of
the engine 1. Thus, the discharge amount estimation unit 71
calculates a basic discharge amount by inputting the engine RPM
that is a parameter for specifying the operation state of the
engine 1 and the intake air amount of the engine 1 into a basic
discharge amount map MP1, calculates a water temperature correction
factor that is 1.0 or higher by inputting an engine water
temperature that is a parameter for specifying an operation state
of the engine 1 into a water temperature correction map MP2, and
further calculates an estimated PM discharge amount by multiplying
the basic discharge amount by the water temperature correction
factor. According to the basic discharge amount map MP1, the basic
discharge amount increases as the intake air amount increases, and
the basic discharge amount increases as the engine RPM becomes
higher as illustrated in FIG. 6. In addition, according to the
water temperature correction map MP2, the water temperature
correction factor has a higher value as the engine water
temperature becomes lower, and the water temperature correction
coefficient approaches 1.0 as the engine water temperature becomes
higher. Therefore, the estimated PM discharge amount increases as
the intake air amount increases; the estimated PM discharge amount
increase as the engine RPM becomes higher; the estimated PM
discharge amount decreases as the engine water temperature becomes
higher.
The PM combustion amount changes according to the PM deposition
amount and the filter temperature of the GPF 33. More specifically,
the PM combustion amount increases as the PM deposition amount
increases and the filter temperature becomes higher. In addition,
the PM combustion amount changes according to an operation state of
the engine 1. Thus, in the combustion amount estimation unit 72, a
PM combustion amount map is defined for each operation state of the
engine 1, wherein the PM combustion amount map outputs the PM
combustion amount per unit time by receiving input of the PM
deposition amount and the filter temperature. More specifically, an
operation state of the engine 1 is divided into a stoichiometric
operation time in which an air-fuel ratio is set as a theoretical
air-fuel ratio, a high load operation time in which an air-fuel
ratio is set to be richer than a theoretical air-fuel ratio, and a
motor drive control time in which air is supplied to the GPF 33
with a fuel injection amount set to 0. In the combustion amount
estimation unit 72, a PM combustion amount map MP3 for the
stoichiometric operation time, a PM combustion amount map MP4 for
the high load operation time, and a PM combustion amount map MP5
for the motor drive control time are defined.
As illustrated in FIG. 6, according to the PM combustion amount map
MP3 for the stoichiometric operation time, the PM combustion amount
increases as the PM deposition amount becomes larger and the filter
temperature becomes higher as described above. In addition, in the
high load operation time, the air-fuel ratio becomes richer than
the theoretical air-fuel ratio, the concentration of oxygen in
exhaust becomes lower than in the stoichiometric operation time,
and thus PM captured in the GPF 33 is hardly combusted. Therefore,
according to the PM combustion amount map MP4 for the high load
operation time, the PM combustion amount is substantially zero
regardless of the PM deposition amount and the filter temperature.
In addition, a larger amount of oxygen is supplied to the GPF 33 in
the motor drive control time than in the stoichiometric operation.
Therefore, according to the PM combustion amount map MP5 for the
motor drive control time, the PM combustion amount is larger than
in the stoichiometric operation time.
The combustion amount estimation unit 72 selects one among the PM
combustion amount maps MP3 to MP5 according to the current
operation state of the engine 1 and calculates an estimated PM
combustion amount by inputting a filter temperature acquired based
on a detection signal of the exhaust temperature sensor 43 and a
previous value of the estimated PM deposition amount into the
selected PM combustion amount map.
The integration unit 73 calculates the estimated PM deposition
amount by integrating the results of subtraction of the estimated
PM combustion amount calculated by the combustion amount estimation
unit 72 from the estimated PM discharge amount calculated by the
discharge amount estimation unit 71.
Returning to FIG. 4, the ECU 7 determines whether the value of an
all-time excessive deposition prevention flag is 1 in S2. The
all-time excessive deposition prevention flag is a flag indicating
that the all-time excessive deposition prevention control (see S5),
which will be described below, is being executed, and is set to 1
when the estimated PM deposition amount is a start threshold or
greater (see S4 which will be described below) and is reset to 0
thereafter when the estimated PM deposition amount is smaller than
an end threshold (see S7 which will be described below) or the
vehicle stops. The ECU 7 proceeds to S3 when the determination
result of S2 is NO and proceeds to S6 when the determination result
is YES.
In S3, the ECU 7 determines whether the estimated PM deposition
amount is the start threshold [g] set for determining an execution
start time of the all-time excessive deposition prevention control
or greater. When the determination result of S3 is YES, the ECU 7
determines that it is time to start the all-time excessive
deposition prevention control, sets the value of the all-time
excessive deposition prevention flag to 1 (see S4), and starts the
all-time excessive deposition prevention control (see S5).
Accordingly, the PM deposition amount gradually decreases
thereafter. Further, the specific procedure for the all-time
excessive deposition prevention control will be described below
with reference to FIG. 7. In addition, when the determination
result of S3 is NO, the ECU 7 proceeds to S8. Further, the start
threshold is set to be equal to or a value close to an allowable
upper limit amount determined to prevent melting damage of the
GPF.
In S6, the ECU 7 determines whether the estimated PM deposition
amount is smaller than the end threshold [g] set to determine an
execution end time of the all-time excessive deposition prevention
control. When the determination result of S6 is NO, the ECU 7
proceeds to S5 to continuously execute the all-time excessive
deposition prevention control. In addition, when the determination
result of S6 is YES, the ECU 7 determines that it is time to end
the all-time excessive deposition prevention control, resets the
value of the all-time excessive deposition prevention flag to 0
(see S7), and proceeds to S8. Here, the end threshold is set to a
value smaller than the above-described start threshold.
Accordingly, when the estimated PM deposition amount exceeds the
start threshold, the all-time excessive deposition prevention
control is executed until the estimated PM deposition amount
becomes the end threshold or smaller.
Next, in S8, the ECU 7 determines whether temperature rise control
for raising the temperature of the engine 1 and exhaust thereof has
been executed from the start of the vehicle to the current time
point. In the temperature rise control, the ECU 7 raises the
temperature of the engine 1 and the exhaust by delaying the spark
time by the spark plug 14, the fuel injection time by the fuel
injection valve 13, or the like to be later than a time determined
at the time of a normal operation. When the temperature rise
control has been executed after the start of the engine 1, the
temperature of the GPF 33 becomes higher than the temperature at
which PM is combusted, and thus it is determined that there is no
concern of excessive deposition occurring in the GPF 33. Thus, when
the determination result of S8 is YES, the ECU 7 immediately ends
the process of FIG. 4 without executing the following process, and
when the determination result is NO, the ECU 7 proceeds to S9.
Further, the ECU 7 increases the temperature of the engine 1,
exhaust, the GPF 33 provided on the exhaust pipe 32, an exhaust
purification catalyst which is not illustrated, and the like by
executing the temperature rise control when the start-time water
temperature is in a temperature rise range between a predetermined
temperature-rise lower limit temperature (e.g., -10.degree. C.) and
a predetermined temperature-rise upper limit temperature (e.g.,
80.degree. C.), and thus promptly increases fuel efficiency and
exhaust purification performance. Further, the temperature rise
control is preferably executed even when the start-time water
temperature is equal to or lower than the temperature-rise lower
limit temperature. However, when the start-time water temperature
is lower than the temperature-rise lower limit temperature, it is
not possible to sufficiently increase the temperature of the engine
1, exhaust, and the like even if the temperature rise control is
executed, and thus there is concern of fuel efficiency
deteriorating. Thus, when the start-time water temperature is equal
to or lower than the temperature-rise lower limit temperature, the
ECU 7 does not execute the temperature rise control. Therefore, the
ECU 7 executes the start-time excessive deposition prevention
control which will be described below (see S10 which will be
described below) at least under the condition that the start-time
water temperature is equal to or lower than temperature-rise lower
limit temperature.
Next in S9, the ECU 7 acquires the start-time water temperature and
determines whether the start-time water temperature is higher than
a predetermined PM generation temperature (e.g., 80.degree. C.).
The PM discharge amount [g/s] of the engine 1 is characteristic in
that it decreases as the start-time water temperature becomes
higher and becomes substantially 0 as the start-time water
temperature becomes higher than the PM generation temperature.
Thus, when the determination result of S9 is YES (i.e., when the
start-time water temperature is higher than the PM generation
temperature), the ECU 7 determines that PM is hardly discharged
from the engine 1 after the start of the engine 1 to the current
time point, and immediately ends the process of FIG. 4 without
executing the following process. In addition, when the
determination result of S9 is NO, the ECU 7 proceeds to S10 and
executes the start-time excessive deposition prevention control.
The specific procedure for the start-time excessive deposition
prevention control will be described below with reference to FIG.
8.
FIG. 7 is a flowchart showing the detailed procedure for the
all-time excessive deposition prevention control. First in S20, the
ECU 7 acquires the filter temperature that is the temperature of
the GPF 33 and determines whether the filter temperature is higher
than or equal to a predetermined PM combustion start temperature
(e.g., 350.degree. C.). If the temperature of the GPF 33 is lower
than the PM combustion start temperature, the motor drive control,
which will be described below, is executed and PM will not be
combusted even if air is supplied to the GPF 33. For this reason,
if the determination result of S20 is NO (i.e., the filter
temperature is lower than the PM combustion start temperature), the
ECU 7 determines that PM will not be combusted in the GPF 33 and
immediately ends the process of FIG. 7 without executing the
following process, and if the determination result is YES, the ECU
7 proceeds to S21.
Next in S21, the ECU 7 determines whether the travel range is the
forward range, the vehicle speed is higher than or equal to a
predetermined reference vehicle speed, and the driving force
required by the driver is smaller than a predetermined reference
driving force. If the travel range is not the forward range or the
vehicle speed is lower than the reference vehicle speed, it is
difficult to supply a sufficient amount of air to the GPF 33 even
if motor drive control is executed, and thus the effect of
combusting PM is small. Since a driving force is not generated by
the engine 1 in motor drive control, if motor drive control is
executed with a driving force required to be greater than a
reference driving force, it is not possible to generate a driving
force according to the required driving force only with the drive
motor TM, power performance of the vehicle V may deteriorate. Thus,
if the determination result of S21 is NO, the ECU 7 immediately
ends the process of FIG. 7 without performing the following
process, and if the determination result is YES, the ECU 7 proceeds
to S22.
Next in S22, the ECU 7 stops fuel injection from the fuel injection
valve 13, executes motor drive control for rotating the crank shaft
17 with the generator motor GM, and ends the process of FIG. 7.
Accordingly, air is supplied to the GPF 33 which has reached at
least a high temperature that is higher than or equal to the PM
combustion temperature, and thus combustion of PM captured by the
GPF 33 is promoted.
FIG. 8 is a flowchart showing the detailed procedure for start-time
excessive deposition prevention control. First in S30, the ECU 7
determines whether the filter temperature is higher than or equal
to the PM combustion start temperature through the same procedure
as the process of S20 of FIG. 7. If the determination result of S30
is NO, the ECU 7 immediately ends the process of FIG. 8 without
executing the following process, and if the determination result is
YES, the ECU 7 proceeds to S31.
Next in S31, the ECU 7 determines whether the travel range is the
forward range, the vehicle speed is higher than or equal to the
reference vehicle speed, and the driving force required by the
driver is smaller than the reference driving force through the same
procedure as the process of S21 of FIG. 7. If the determination
result of S31 is NO, the ECU 7 immediately ends the process of FIG.
8 without executing the following process, and if the determination
result is YES, the ECU 7 proceeds to S32.
Next in S32, the ECU 7 calculates the PM combustion integration
amount [g] corresponding to the estimated value of the integration
amount of PM combusted in the GPF 33 from the engine start to the
current time point, and proceeds to S33.
FIG. 9 is a diagram illustrating the detailed procedure for
calculating the PM combustion integration amount by the ECU 7. The
ECU 7 calculates the PM combustion integration amount by acquiring
the filter temperature acquired based on the detection signal of
the exhaust temperature sensor 43 and the operation state of the
engine 1 and repeatedly executing the arithmetic operation shown in
FIG. 9 based on the filter temperature and the operation state in
every predetermined control period.
The ECU 7 calculates the PM combustion integration amount using the
PM combustion amount maps MP3 to MP5 described with reference to
FIG. 6. More specifically, the ECU 7 calculates the PM combustion
amount by selecting one among the PM combustion amount maps MP3 to
MP5 according to the current operation state of the engine 1 and
inputting the filter temperature acquired based on the detection
signal of the exhaust temperature sensor 43 and the PM deposition
amount into the selected PM combustion amount map and calculates
the PM combustion integration amount by integrating the PM
combustion amounts.
Further, when calculating the PM combustion integration amount
using the PM combustion amount maps MP3 to MP5, it is desirable for
the ECU 7 to input an allowable upper limit amount that is a
predetermined fixed value to the PM combustion amount maps MP3 to
MP5, rather than the actual PM deposition amount as a PM deposition
amount. In other words, it is desirable for the ECU 7 to calculate
the PM combustion integration amount on the assumption that the
allowable upper limit amount of PM has been deposited in the
filter. Since the greater the PM deposition amount is in the GPF
33, the greater the PM combustion amount is for the GPF 33 as
described above, the PM combustion integration amount is estimated
to be greater than the actual amount. Thus, the execution frequency
of motor drive control (see S35), which will be described below,
becomes lower than the case in which the PM combustion integration
amount is calculated using the actual PM deposition amount, and
therefore, waste of energy such as a fuel and electric power for
executing motor drive control can be curbed accordingly. However,
while there is concern of the PM deposition amount increasing in
the GPF 33 due to the low execution frequency of motor drive
control in this case, the PM combustion integration amount is
calculated on the assumption that the allowable upper limit amount
of PM has been deposited in the GPF 33 as described above, and thus
it is possible to prevent the actual PM deposition amount from
exceeding the allowable upper limit amount.
Returning to FIG. 8, in S33, the ECU 7 calculates the PM discharge
integration amount [g] that is the threshold with respect to the PM
combustion integration amount and proceeds to S34. The PM discharge
integration amount corresponds to the estimated value of the
integration amount of PM discharged from the start of the engine
1.
FIG. 10 is a diagram illustrating the detailed procedure for
calculating the PM discharge integration amount by the ECU 7. The
ECU 7 calculates the PM discharge integration amount based on an
engine RPM, an intake air amount of the engine 1, and an engine
water temperature. More specifically, the ECU 7 calculates the PM
discharge integration amount using the basic discharge amount map
MP1 and the water temperature correction map MP2 described with
reference to FIG. 6. More specifically, the ECU 7 calculates the
basic discharge amount by inputting the engine RPM and the intake
air amount into the basic discharge amount map MP1, calculates a
water temperature correction factor by inputting the engine water
temperature into the water temperature correction map MP2,
calculates the estimated PM discharge amount by multiplying the
basic discharge amount by the water temperature correction factor,
and further calculates the PM discharge integration amount by
integrating the estimated PM discharge amounts.
Returning to FIG. 8, in S34, the ECU 7 determines whether the PM
combustion integration amount calculated in S32 is less than the PM
discharge integration amount calculated in S33. If the
determination result of S34 is YES, the ECU 7 proceeds to S35,
stops fuel injection from the fuel injection valve 13, executes
motor drive control for rotating the crank shaft 17 with the
generator motor GM, and ends the process of FIG. 8. Accordingly,
since air is supplied to the GPF 33 that has reached at least a
high temperature that is higher than or equal to the PM combustion
temperature, and thus combustion of PM captured by the GPF 33 is
promoted. In addition, if the determination result of S34 is NO,
the ECU 7 immediately ends the process of FIG. 8 without executing
motor drive control.
FIG. 11 is a time chart illustrating a specific example of
excessive deposition prevention control described above. In FIG.
11, the PM deposition amount, the engine water temperature, the
execution and non-execution of the all-time excessive deposition
prevention control, and the execution and non-execution of
start-time excessive deposition prevention control through the 4
driving cycles (times t0 to t1, times t1 to t4, times t4 to t6, and
times t6 to t9) are illustrated.
In the driving cycle of the times t0 to t1, the start-time water
temperature is lower than the temperature-rise lower limit
temperature that is the lower limit of the temperature range in
which temperature rise control is executed. In this case, since the
PM discharge amount immediately after the start of the engine 1 is
large and temperature rise control has not been executed, the
filter easily enters the excessive deposition state as described
with reference to FIG. 5. For this reason, the ECU 7 executes the
start-time excessive deposition prevention control (see S10) in the
driving cycle of the times t0 to t1. In the start-time excessive
deposition prevention control, the motor drive control is executed
(see S35) if the predetermined conditions (see S30 and S31) are
satisfied and the PM combustion integration amount is smaller than
the PM discharge integration amount (see S34), and thus combustion
of PM in the GPF 33 is promoted to avoid the excessive deposition
state.
Since the start-time water temperature is higher than the
temperature-rise lower limit temperature in the driving cycle of
the times t1 to t4, the start-time excessive deposition prevention
control is not executed in the driving cycle of the times t1 to t4.
In addition, in this driving cycle, the ECU 7 executes the all-time
excessive deposition prevention control at the time t2 according to
the PM deposition amount exceeding the start threshold set close to
the allowable upper limit amount (see S5). In the all-time
excessive deposition prevention control, the ECU 7 executes the
motor drive control (see S22) when the predetermined conditions
(see S20 and S21) are satisfied, and thus the combustion of PM in
the GPF 33 is promoted to avoid the excessive deposition state.
After the all-time excessive deposition prevention control is
started as described above, the ECU 7 ends the all-time excessive
deposition prevention control (see S6) at the time t3 according to
the PM deposition amount lower than an end threshold.
Since the start-time water temperature is higher than the
temperature-rise lower limit temperature in the driving cycle of
the times t4 to t6, the start-time excessive deposition prevention
control is not executed in the driving cycle of the times t4 to t6.
In addition, in the driving cycle, the ECU 7 executes the all-time
excessive deposition prevention control (see S5) at the time t5
according to the PM deposition amount exceeding the start
threshold. Accordingly, while the PM deposition amount turns to
decrease as in the driving cycle of the times t1 to t4, the vehicle
stops before the PM deposition amount reaches the end threshold at
the time t6. In this case, the ECU 7 resets the value of the
all-time excessive deposition prevention flag to 0 as described
above. Thus, in the next driving cycle, the all-time excessive
deposition prevention control is not continuously executed.
Since the start-time water temperature is higher than the
temperature-rise lower limit temperature in the driving cycle of
the times t6 to t9, the start-time excessive deposition prevention
control is not executed in the driving cycle of the times t6 to t9.
In addition, since the PM deposition amount exceeds the start
threshold at the time t7 in this driving cycle, the ECU 7
thereafter executes the all-time excessive deposition prevention
control (see S5) at the time t8 until the PM deposition amount
becomes smaller than the end threshold.
The following effects can be exhibited according to the vehicle V
of the present embodiment. (1) The vehicle V performs the motor
drive control (see S35) for rotating the crank shaft 17 of the
engine 1 with the generator motor GM if a filter temperature is
higher than or equal to the PM combustion start temperature and the
PM combustion integration amount is smaller than the PM discharge
integration amount. Accordingly, in the state in which the PM
combustion integration amount is smaller than the PM discharge
integration amount, that is, when PM needs to be actively combusted
to prevent excessive deposition, the motor drive control is
executed, and combustion of PM deposited in the GPF 33 can be
promoted. In addition, in the state in which the PM combustion
integration amount is greater than or equal to the PM discharge
integration amount, that is, the state in which most PM captured in
the GPF 33 has already been combusted and excessive deposition has
not occurred, the motor drive control can be prevented.
Accordingly, waste of energy such as a fuel and electric power for
executing the motor drive control can be curbed.
(2) PM particularly increases immediately after the start of the
engine 1 and is discharged from the engine 1. Thus, the ECU 7
calculates the PM combustion integration amount that is the
integration amount of PM combusted in the GPF 33 in the period
immediately after the start of the engine when a particularly large
amount of PM can be discharged to the current time point, and
executes the motor drive control by comparing the PM combustion
integration amount with the PM discharge integration amount.
Accordingly, the motor drive control can be executed at the right
time and further waste of energy needed for executing the motor
drive control can be curbed. In addition, the ECU 7 assumes that
the allowable upper limit amount of PM has been deposited in the
GPF 33 when calculating the PM combustion integration amount.
Accordingly, the execution frequency of the motor drive control is
lower than when the PM combustion integration amount is calculated
using the actual PM deposition amount according to the present
embodiment, and thus waste of energy such as a fuel and electric
power for executing the motor drive control can be curbed
accordingly. However, while there is concern of the PM deposition
amount increasing in the GPF 33 due to the low execution frequency
of the motor drive control in this case, the PM combustion
integration amount is calculated on the assumption that the
allowable upper limit amount of PM has been deposited in the GPF 33
in the above-described present embodiment, and thus it is possible
to prevent the actual PM deposition amount from exceeding the
allowable upper limit amount.
(3) The ECU 7 calculates the PM combustion integration amount based
on the filter temperature and the operation state of the engine 1
which are correlated with the PM combustion integration amount.
Accordingly, since the PM combustion integration amount can be
calculated with high accuracy, the motor drive control can be
executed at the right time, and further waste of energy needed for
executing the motor drive control can be curbed.
(4) As described with reference to FIG. 5, the integration amount
of PM discharged from the start of the engine 1 significantly
increases in the process of warm-up of the engine. Thus, the ECU 7
sets the PM discharge integration amount that is the integration
amount of PM discharged from the start of the engine as a threshold
with respect to the PM combustion integration amount and determines
whether to execute the motor drive control (see S34). Accordingly,
in the process of warm-up of the engine 1 in which the PM
deposition amount is likely to significantly increase, the motor
drive control can be executed at the right time.
(5) The ECU 7 calculates the PM discharge integration amount based
on the engine RPM, the intake air amount, and the engine water
temperature. Accordingly, since the PM discharge integration amount
can be calculated with high accuracy, the motor drive control can
be executed at the right time, and further waste of energy needed
for executing the motor drive control can be curbed.
(6) When the start-time water temperature is in the
temperature-rise range between the temperature-rise lower limit
temperature and the temperature-rise upper limit temperature, the
ECU 7 raises the temperatures of the engine 1 and exhaust thereof
by executing the temperature rise control and further improves the
exhaust purification performance of the GPF 33. In addition, the
temperature of exhaust increases when the temperature rise control
is executed, and thus PM captured in the GPF 33 is combusted as
well. However, when the start-time water temperature is lower than
the temperature-rise lower limit temperature, it is not possible to
improve the exhaust purification performance in an early stage even
if the temperature rise control is executed, there is concern of
fuel efficiency deteriorating, and therefore, the ECU 7 does not
execute the temperature rise control. Thus, when the start-time
water temperature is equal to or lower than the temperature-rise
lower limit temperature and the temperature rise control is not
executed, the ECU 7 performs the motor drive control. Accordingly,
excessive deposition in the GPF 33 can be prevented at the time of
a low-temperature start of the vehicle V at which the PM deposition
amount easily increases in the GPF 33.
(7) When the start-time water temperature is in the
temperature-rise range as described above, while the temperature
rise control is executed, the PM deposition amount of the GPF 33
may gently increase and exceed the allowable upper limit amount.
Thus, when the PM deposition amount exceeds the start threshold set
near the allowable upper limit amount in a state in which the
start-time water temperature is higher than or equal to the
temperature-rise lower limit temperature, the ECU 7 performs the
motor drive control until the PM deposition amount becomes equal to
or smaller than the end threshold. Accordingly, it is possible to
prevent the PM deposition amount from greatly exceeding the
allowable upper limit amount.
(8) When the filter temperature is higher than or equal to the PM
combustion start temperature and the PM combustion integration
amount is smaller than the PM discharge integration amount, the ECU
7 performs the motor drive control for rotating the crank shaft 17
with the generator motor GM. Accordingly, the motor drive control
can be performed at the right timing to prevent the saturated
deposition amount from exceeding the allowable upper limit amount,
that is, the GPF 33 does not come into the excessive deposition
state.
(9) The ECU 7 executes the motor drive control on the condition
that the travel range is the forward range, the vehicle speed is
higher than or equal to the predetermined reference vehicle speed,
and the required driving force is smaller than the predetermined
reference driving force. Accordingly, the motor drive control can
be executed without lowering the power performance of the vehicle,
and further PM can be effectively combusted through the motor drive
control.
Although the embodiment of the present disclosure has been
described above, the present disclosure is not limited thereto.
Detailed configurations of the present disclosure may be
appropriately modified in the scope of the gist of the present
disclosure.
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